The class of polymers of carbon monoxide and olefin(s) has been known for a number of years. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical catalysts, e.g., peroxy compounds. U.K. Pat. No. 1,081,304 produced similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium salts as catalyst. Nozaki extended the process through the use of triarylphosphine complexes of palladium salts and certain inert solvents, e.g., U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, also known as polyketones, has become of greater interest because of the greater availability of the polymers. The polymers have been shown to be of the formula --CO--A-- wherein A is the moiety of unsaturated hydrocarbon polymerized through the ethylenic unsaturation. For example, when the ethylenically unsaturated hydrocarbon is ethylene, the polymer is represented by the formula --CO--CH.sub.2 --CH.sub.2 --.
It is known that the nature of the phosphine or other complexing ligand employed has a considerable influence on the efficiency of the polymerization process. More recent polyketone polymerization processes employ a bidentate ligand of phosphorus, arsenic or antimony in combination with a palladium compound and the anion of a non-hydrohalogenic acid of a pKa less than about 6, preferably less than about 2. Such processes are illustrated by published European Patent Applications Nos. 0,121,965 and 0,181,014 and by copending U.S. patent application Ser. No. 930,468, filed Nov. 14, 1986 (Docket No. K-0722).
Within the earlier work of Nozaki with monodentate phosphines considerable differences in activity were found which could be attributed to the triarylphosphine ligand employed. In the catalyst complexes of U.S. Pat. No. 3,694,412, as shown in Table 1, column 4, good results are obtained with triphenylphosphine-based catalysts and also when the phenyl groups were substituted in the para or the meta positions. However, use of an ortho-substituted phenyl phosphine did not produce measurable amounts of polymer and the use of the ortho-substituted triphenyl phosphines was discouraged.
Although quite satisfactory yields of polyketones are produced with use of the bidentate phosphorus ligands employed in conjunction with a palladium compound and the anion of a strong non-hydrohalogenic acid, it would be of advantage to have available a more simple catalyst composition.